Direct measurement of the orbital angular momentum mean and variance in an arbitrary paraxial optical field

TL;DR

This paper presents a novel experimental method to measure the mean and variance of orbital angular momentum in paraxial optical fields efficiently, reducing complexity and enabling new applications in optical manipulation and communication.

Contribution

The authors introduce a direct measurement technique for OAM mean and variance that avoids full spectrum analysis, simplifying experimental procedures.

Findings

Successfully measured OAM mean and variance simultaneously

Reduced measurement complexity from full spectrum analysis to two measurements

Potential applications in optical torque measurement and communication

Abstract

We introduce and experimentally demonstrate a method for measuring at the same time the mean and the variance of the photonic orbital angular momentum (OAM) distribution in any paraxial optical field, without passing through the acquisition of its entire angular momentum spectrum. This method hence enables one to reduce the infinitely many output ports required in principle to perform a full OAM spectrum analysis to just two. The mean OAM, in turn, provides direct access to the average mechanical torque that the optical field in any light beam is expected to exert on matter, for example in the case of absorption. Our scheme could also be exploited to weaken the strict alignment requirements usually imposed for OAM-based free-space communication.